The present invention relates to electronic throttle control and, more specifically, to a method and apparatus for operating a throttle plate motor in a throttle plate assembly equipped with opposing return springs.
In internal combustion engine control, the movement of the throttle plate or blade by an electric motor which controls the opening and closing of the throttle plate through an angle corresponding to the amount of depression of an accelerator pedal is generally known. Typically, such control includes an actuator connected to a throttle valve or plate, such as a conventional butterfly valve, wherein valve position is adjusted by controlled actuator motion to provide appropriate restriction on the air passage into the engine. The actuator is in communication with a controller, which controls actuator motion when air is to be metered to the engine.
The controller may be responsive to any one of several factors used to formulate the current desired throttle position. For example, such factors may include inputs indicative of the engine operating conditions, an operator command from an accelerator pedal, information from an active cruise control algorithm, an active idle speed control algorithm, or an active traction control algorithm. Further, feedback may be provided to the controller from a conventional throttle valve position sensor communicating a signal to the controller, the magnitude of which is related to the degree of opening of the throttle valve or plate. Corrective positioning of the actuator or diagnostics may be carried out by the controller in response to the sensor feedback signal. At least one, and possibly two, opposing return springs act on the throttle plate to return the throttle plate to a default position in the absence of throttle control. This default position is generally selected so that if a fault is detected and the throttle de-energizes, the vehicle can run in a controlled limp home mode.
In internal combustion engines using electronic throttle control, it is desirable that the throttle plate position accurately track the accelerator pedal position with a high-speed response capability. However, the response capability of a throttle plate is affected by the return spring characteristics, including static spring forces, non-uniform spring constants and variations in the spring force of the springs over the full range of spring compression.
Thus, it would be desirable to provide a method for operating an electronic throttle position drive motor having opposing return springs which improves response in prior electronic throttle plate drive motor control with respect to variations in return spring characteristics.
The present invention adds unique compensation for return spring characteristics used in an electronic throttle position control for an internal combustion engine to improve the response of throttle position changes.
According to one aspect of the invention, a method controls an internal combustion engine throttle valve or plate by an actuator which is responsive to at least accelerator pedal position and throttle plate position. The throttle plate has opposing springs acting on the throttle plate to normally bias the throttle plate to a default position.
The method comprises the step of compensating for one of spring characteristics and static friction of the springs when moving the throttle plate to -a desired position within the range of movement of the throttle plate. Preferably, the method compensates for both the spring characteristics and static friction. More preferably, compensation is provided for spring characteristics, including at least one of static spring and non-linear spring forces.
The present method also learns the force characteristics of the springs over the range of movement of the springs.
In another aspect of the invention, an apparatus controls a throttle plate for controlling a throttle plate driven by an actuator. The apparatus includes means for sensing throttle plate position and a control for determining a desired throttle position. An actuator is responsive to the control for driving the throttle plate to the desired throttle position. The control includes compensating means for compensating for one of return spring characteristics and static friction of the throttle plate and return springs encountered when moving the throttle plate to the desired throttle position.
The compensating means includes means for compensating for static spring forces in the return springs and static friction of the return springs and the throttle plate.
Means are also provided for learning the spring force characteristics so as to adjust the spring force compensation based on variations in the construction of the return springs and wear during use of the return springs.
Implementation of the method and apparatus of the present invention uniquely provides compensation for various spring and friction related characteristics affecting responsive movement of a throttle plate to actuator commands. The method and apparatus also uniquely learn the spring characteristics, which, may vary from spring to spring and/or vary over time, to provide accurate compensation and throttle plate response.